Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A wet nurse is a woman hired to breast feed and care for another's child. Wet nurses are hired when the mother is unable or chooses not to nurse the child herself. Wet-nursed children may be known as "milk-siblings", and in some cultures the families are linked by a special relationship of milk kinship. Mothers who nurse each other's babies are engaging in a reciprocal act known as cross-nursing or co-nursing. A wet-nurse may be employed if the mother of a baby is unable or elects not to breast-feed her infant. A common reason historically, which still exists in a few situations today, is simply one of social expectations and status. Other reasons range from serious or chronic illnesses such as cancer and their treatment to temporary difficulties nursing. Additionally, a mother's taking (prescription or illegal) drugs may necessitate a wet-nurse if a drug in any way changes the content of her milk.